Magnetic field sensors employ a variety of types of magnetic field sensing elements, for example, Hall effect elements and magnetoresistance elements, often coupled to a variety of electronics, all disposed over a common substrate. A magnetic field sensing element (and a magnetic field sensor) can be characterized by a variety of performance characteristics, one of which is a sensitivity, which can be expressed in terms of an output signal amplitude versus a magnetic field to which the magnetic field sensing element is exposed.
The sensitivity of a magnetic field sensing element, and therefore, of a magnetic field sensor, is known to change in relation to a number of parameters. For example, the sensitivity can change in relation to a change in temperature of the magnetic field sensing element. As another example, the sensitivity can change in relation to a mechanical stress (or “strain”) imposed upon the substrate over which the magnetic field sensing element is disposed. Such stress can be imposed upon the substrate at the time of manufacture of an integrated circuit containing the substrate. For example, the strain can be imposed by stresses caused by curing of molding compounds used to form an encapsulation of the substrate, e.g., a plastic encapsulation.
It will be recognized that changes in the temperature of a magnetic field sensor can directly result in changes of sensitivity due to the changes of temperature. However, the changes in the temperature of the magnetic field sensor can also indirectly result in changes of sensitivity where the temperature imparts strains upon the substrate over which the magnetic field sensing element is disposed.
The changes in sensitivity of the magnetic field sensor and of the magnetic field sensing element are undesirable.